Fabrication and measurement of low-stress polyimide membrane for high-resolution variable optical attenuator

We have fabricated low-stress polyimide membranes for use as high-resolution variable optical attenuator (VOA). Polyimide membranes are assembled with fiber collimators to perform 3-D beam spoiling that varies the optical power with 0.01-dB resolution. The measured residual stress and Young's modulus of the polyimide membrane are 3.2 MPa and 15 GPa, respectively. The 41-mu m deformation of the membrane is demonstrated by the electrostatic force with 170 volts. The 0.46-dB insertion loss and > 15-dB dynamic range are achieved at 1550-nm wavelength.